Magnesium base alloy



Patented July 26, 1938 i v 4 UNITED, STATES PATENT OFFICE MAGNESIUM missALLOY John A. Gann, Midland, Mien, assignor to The Dow Chemical Company,Midland, Mich., a corporation of Michigan No Drawing. Application August2, 1937, Serial 3 Claims. (Cl. 75168) The present invention relates tomagnesium 9.1- Solution heat treated alloys loys and more particularlyto those in which magnesium is the predominant constituent. Nominalcomposition in perjcent Most of the present commercial uses for mag-(MFmmainde') 'fg gg Yield strength nesium alloys are due to their highstrength and lhlsq. in.

high strength-weight ratio. If these character M ed istics could befurther improved, the field of application of these light weight alloyswould be 0 2 0.2 32,000 10,000 greatly extended. g 81% i The principalobject of this invention is to produce magnesium alloys having improvedphysical 3 3 81% 3;;33 3:383 properties. A more specific object is toproduce 2 s 0.2 e 34,000 12,200 magnesium alloys that are amenable toheat treatment. Other objects and advantages will appear Solution heattreated and aged u as the description proceeds.

This invention is based on the discovery that the 6 Q 2 32, 900 10 200properties of magnesium-aluminum-cadmium- 0 2 0 2 37,500 14,900manganese alloys as described in United States 3 3 3% g 33% $1288 PatentNo. 1,959,913 may be improved to a very d marked extent by the additionof relatively small 3 g 8:; g:% I ,25% amounts of zinc, withoutappreciably increasing 2 8 6 37,000 19,200 the specific gravity of thealloy. I have discoved a maximum p ty improvement is I have likewisediscovered that the addition tained when these alloys are subjected tothe well of zinc t magnesjm-aluminum-cadjum-manga..

known methods of solution heat treatment and nese alloys has resulted ina marked improvement solution heat treatment plus aging. I have also 'incorrosion resistance. This beneficial effect oi.' found that theadvantages occurring from the ad- Z c s Particularly PrOhOlmCed in the sOf the dition of zinc are present when approximately cast and thesolution heat treated and aged y 0,5 t 3 per cent 1 zinc are added tomagnesium although it is evident in some of the solution heat alloyscontaining from about 1 to 12 per cent of treated alloysh followingtable illustrates aluminum, f about 0 to 10 per cent of this improvementas obtained from alternate immium, and from about 0.1 to 05. per cent ofmersion tests conducted for one week in a 3 per mangane-Se 7 cent saltsolution.

Specific examples of the property improvements that result in theproduction of my new alloy by Nmniml in am. Loi it .da

adding zinc to the well known magnesium-aim" 825 8 mm as nwegh mg/cm yminum-cadmium-manganese alloys'are shown in thefollowing tables whereillustrations are given M e Mn Zn cast i S P H TI of cast, solution heattreated, and solution heat treated and aged alloys. 6 2 M L94 n1 2 i at:2'? 2;: cast e 2 012 0 0:50 8:0 24.7

Nominal composition in percent 1 S. H. 'l.=8olution heat treated. i(Mg=remainder) l a'tlensgitlie1 Yied strength I S. P. H. T.-=Solutlonheat treated and aged.

ran 1 I -l q- I have furthermore discovered that if my im- M ed M-proved alloy likewise contains approximately 0.5

I to 10 per cent oi! lead, or, in other words, if the g g 3:; 2 33 $133improved alloy-is obtainedby adding both lead 2 8 o 2 25 200 and zinc tothe magnesium-aluminum cadmi-um- 2 s 012 4 281700 manganese alloy, thatthe resultant composition 2 8 6 10,200 is superior to that obtained whenonly one of the v metals, lead or zinc, is added to the known mairnesiumaluminum cadmium manganese alloy. 1 This is illustrated, for example, bythe yield strength and hardness data in the following table:

Nominal composltion in per cent (Mg= remam- Yield Brine] der) Conditionstrength, hardlb./sq. in. ness Al Cd Mn Pb Zn 1 S. H. T.=Solution heattreated. l S. P. H. T.=Solution heat treated and aged.

When the alloy is to be used for the production of castings, I normallyprefer to use compositions containing approximately 85 to 92 per cent ofmagnesium, from 4 to 10 per cent of aluminum, 3 from 1 to 6 per cent ofcadmium, from 0.1 to 0.3 percent of manganese, and from 2 to 6 per centof zinc. Where lead is likewise required, it should be present inamounts ranging from about 1 to 6 per cent. When the alloy is to be usedin plastic deformation operations it should, in general, contain 90 to96 per cent of magnesium, and the various alloying elements in thefollowing proportions: 1 to 8 per cent of aluminum, 0.5 to 3- per centof cadmium, 0.1 to 0.5 per cent 'of manganese, 0.5 to 2 per cent oflead, and 0.5 to 2 per cent of zinc.

My new polynary alloys may be prepared by the methods usually employedfor melting and alloying metals with magnesium, such as adding therespective alloying metals singly or jointly to a bath of moltenmagnesium protected from oxidation by a cover of fluid flux. Thesolution heat treatment for the zinc-free alloys may consist in heatingthe material for 20 hours at 430 (3., followed byair cooling, or, whenzinc is present in the alloy, 12 hours at 320 C. plus 16 hours at 420C., followed by air cooling. The aging treatment consists ofapproximately 16 hours heating at 175 C., subsequent to the abovesolution heat treatment. Plastic deformation operations, such asextruding, forging, and rolling are best conducted at temperaturesbetween 300 and 5 I Other modes of applying the principle of myinvention may be employed instead of those explained, change being madeas regards the ingredients and the steps herein disclosed, pro- 20 videdthose stated by any of the following claims or their equivalent beemployed.

I particularly point out and distinctly claim as my. invention I 1. Amagnesium-base alloy containing from ap- 'ance being magnesium.

2. A magnesium-base alloy consisting of approximately 4 to 10'per centof aluminum, and from about 1 to 6 per cent of cadmium, and from about0.1 to 0.3 per cent of manganese, and from about 2 to 6 per cent ofzinc, the balance being' magnesium.

3. A magnesium-base alloy consisting of approximately 6 per cent ofaluminum, and 2 per cent of cadmium, and 0.2 per cent of manganese, and2 per cent of zinc, the balance being 40 magnesium.

JOHN A. GANN.

